Non-massing tougheners for polyamides

ABSTRACT

The present invention relates to polymeric co-grafting of massing polymers and copolymers of ethylene and one or more α-olefins having at least 4 carbon atoms. The co-grafts are useful tougheners for polyamides.

This application claims the benefit of U.S. Provisional Application No.60/064,747, filed Nov. 7, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel polymeric compositions producedby co-grafting ungrafted polymeric blends and to toughened polyamide andmaterial containing such tougheners.

2. Description of Related Art

There is considerable prior art concerned with improving the impactstrength of polyamides. See for example, British Pat. No. 998,439 orEpstein, U.S. Pat. No. 4,174,358. See also Nylon Plastics, E. I. Kohan(1973, p. 346).

Improvement of impact strength of polyamide resins has long been ofinterest, for resistance to shattering or brittle breaking on impact ofpolyamide molded articles is a desirable feature of any molded article.By “ductile” is meant that cracks do not tend to propagate from the areaof impact, and thus a resin having good ductility is one that isresistant to crack propagation caused by impact. The ductility of anarticle can also be measured by notched Izod test ASTM D-256-73.

A variety of additives have been added heretofore to polyamide resins toimprove strength and ductility. For example, Epstein U.S. Pat. No. '358describes improving impact strength and ductility by adding a selectedrandom copolymer which reacts with the polyamide. However, the tendencyof polyamides in general to break on impact in a brittle fashionincreases as temperatures are lowered. Thus the use of molded articlesfor low temperature applications, such as winter sports equipment,automobile bumpers, and the like, is decreased.

U.S. Pat. No. 5,346,963 generally discloses the grafting of certainmetallocene produced substantially linear ethylene polymers anddiscloses blends of this grafted material with either grafted orungrafted thermoplastic polymers including HDPE, LDPE, LLDPE, ULDPE,polypropylene, EPDM and a host of other polymers. There is no teaching,however, of a composition or blend produced from co-grafting a blend ofmetallocene substantially linear ethylene polymers and eithermetallocene or non-metallocene produced polymers or copolymers such aspolyethylene. Minor levels of polyethylene are sometimes used asexcipients or additives in pre-graft polymers.

The present invention is an improvement over the compositions disclosedin the Epstein patent and subsequent nylon toughener patents, in that ithas been found that certain polyamides, when toughened with certaincompositions as claimed herein which have been prepared from cograftingblends of copolymers of ethylene with one or more α-olefins having atleast 4 carbon atoms and polymers having a tendency to mass (“massingpolymers”) such as EPDM or EPR (metallocene or otherwise) or otherpolymers which mass or agglomerate with grafting agents known in the artyield fabricated parts made from such blends having high impactresistance as well as other beneficial physical properties. Applicantsbelieve the “co-graft” of this blend of ethylene-α-olefin and “massingpolymers” is separate and distinct from a simple blend or mixture ofgrafted ethylene-α-olefin and grafted massing polymers.

In addition, the present inventors have discovered a process which is asignificant improvement over the processes for making modified polymericcompositions and nylon toughened materials containing such compositionswhich relates to elimination of a partitioning agent such aspolyethylene dust which has heretofore been necessary to eliminatemassing. In particular, carboxylic acid or anhydride modified EPDM andEPR are commonly used as tougheners for polyamide. However due to thetacky nature of non-metallocene EPDM and EPR or any metallocene ornon-metallocene polymer which has amorphous or tacky properties, pelletsof these unmodified or acid or anhydride modified polymers are generallycoated with a small amount (up to 10 wt %) of a partitioning agent, suchas talc, carbon black or PE dust to make them free flowing. The additionof the partition agent is generally a costly and cumbersome step. Thismeans an extra step in the modification process. Extra equipment isrequired to introduce the partitioning agent. Further, the quality ofthe modified polymer may suffer due to either too much or too little ofthe partitioning agent. Too little partitioning agent may result inmassing of the product creating handling difficulties in the nyloncompounding step. Too much powder may have a detrimental effect on theperformance of the product as toughener for nylon. Even if applied inthe appropriate amount, the partitioning agent may segregate duringshipping, rendering it ineffective.

Thus, the present inventors have found a way of eliminating the need toadd a partitioning agent to either pre-modified or modified EPDM or EPRor other modified massing polymer in the modification process whilesurprisingly retaining the excellent performance of the product astoughener for polyamide.

As discussed above, the use of modified EPDM or EPR as the tougheningagent for polyamide is well known, see for example, Epstein (U.S. Pat.No. 4,174,358, Nov. 13, 1979). This and subsequent art which uses EPDMor EPR is characterized by the need to use a partitioning agent or toselect an EPDM or EPR with increased crystallinity which does not have atendency to mass.

By using a blend of a copolymer of ethylene and one or more α-olefinshaving at least 4 carbon atoms and an ethylene copolymer having atendency to mass as a substrate in the inventors' improved process, itwas found that a non-massing functional polymer is obtained. By suitablychoosing the concentration of the copolymer of ethylene and one or moreα-olefins having at least 4 carbon atoms, the density of this componentand the graft level of the resulting polymer blend as described herein,the product can be used as a toughener for polyamide.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a composition which comprises orconsists essentially of a carboxylic acid or anhydride modified mixtureof any metallocene or conventional ethylene copolymer having a tendencyto mass (“massing polymer”), and a copolymer of ethylene and one or moreα-olefins having at least 4 carbon atoms (4-10C) (“Composition A”)wherein the composition is produced by modifying (co-grafting) a blendof such “massing polymer” and ethylene-α-olefin copolymer. The ratio ofethylene α-olefin to the “massing polymer” such as EPDM or EPR may befrom about 10:90 to about 90:10.

Surprisingly and unexpectedly, the pre-modified blend which is thensubsequently modified with a typical modifier such as maleic anhydrideto typical levels or more (e.g., 0.3 to 2% by weight) provides goodtoughening properties and non-massing properties or non-massingcharacteristics without loss of low temperature toughness. Theproperties will vary depending upon the particular pre-grafted polymers.In particular, the use of the ethylene α-olefin in the pre-grafted blendeliminates the need for either a pre-modification or post-modificationpartitioning agent.

The present invention more particularly relates to a compositioncomprising a copolymer of ethylene and one or more α-olefins having atleast 4 carbon atoms wherein the copolymer has a density range of0.930-0.880 and a Melt Index (MI) of 0.01-50 and a metallocene ornon-metallocene produced plastomer having a tendency to mass with, inthe case of a conventional (non-metallocene) polymer, has a density of≦0.88 and, in the case of a metallocene, has a density of ≦0.88 which isco-grafted to form the composition of the invention. This composition isthen utilized as a component for blending with olefinic or non-olefinicmaterials ad defined in U.S. Pat. No. 5,346,963, which is herebyincorporated by reference. The blended composition is then utilized fora number of purposes including, for example, toughening polyamide (Nylon6 or Nylon 6,6 or the like) but it may also be utilized in othercompositions or blends or materials. The mixture in the preferred caseis useful as a toughener for polyamide compositions.

The toughened polyamide composition generally comprises, (a) polyamide;(b) composition (A) and optionally, (c) toughening acceptable excipientswhich are selected from additives such as stabilizers and inhibitors ofoxidative, thermal and ultraviolet light degradation; lubricants andmold release agents; colorants including dyes and pigments, fibrous andparticulate fillers and reinforcement, nucleating agents, plasticizers,etc. Composition (A) is useful as a toughener for polyamide or as anadditive to form blends with elastomeric or thermoplastic olefinic ornon-olefinic polymers. Representative of the non-olefin polymersinclude, for example, polymers such as polyesters, polyamides,polycarbonates, polyvinyl chloride, epoxies, polyurethanes and the like.The compositions containing composition (A) and the thermoplasticolefinic or non-olefinic polymers are useful in a wide range of end-useor intermediate use applications including packaging, industrialapplications and the like. For molded articles, like engineeredmaterials, composition (A) is preferably blended with polyamides.

In one embodiment, the manufacturing process to make (A) is superiorover the existing process of modifying massing polymers such as EPDM orEPR because no dusting of the product is required. Thus the need to useextraneous and costly partition agent in the product is eliminated,resulting in a better quality and more consistent product.

The present invention is also preferably a thermoplastic compositioncomprising or consisting essentially of a semi-crystalline polyamidematrix resin such as Nylon 6,6 or Nylon 6 and copolymer, particles ofComposition A dispersed in the polyamide matrix resin. The polyamide maybe present in the composition in an amount, for example, of about 75% to85% by weight of the composition in the preferred case. Of course, thesepercentages can vary from 3% Composition A and 97% polyamide to 40%Composition A and 60% polyamide. The copolymeric blend has particlesthat are dispersed substantially uniformly throughout the polyamide.Amorphous polyamide may also be used.

The copolymeric materials have a melt flow index of between about 0.01to 50 dg/min at 190° C., 2.16 Kg weight. The composition of thecopolymeric blend comprises either (a) 10-90% by weightethylene-α-olefin having at least 4 carbon atoms (e.g., polyethylene),(b) 90-10% by weight of a massing polymer, wherein both (a) and (b) aregrafted with an olefinic carboxylic acid or anhydride or other graftingreagents known to those of skill in the art in an amount of 0.05 to 5 wt%, preferably 0.1 to 3 wt % and most preferably 0.3 to 2 wt % of thecopolymeric blend. These co-grafted blends are then combined with thepolyamide(s) and other excipients to form a toughened composition. Thecopolymeric materials are present in the toughened composition in anamount of at least 1% by weight of the composition. The copolymericmaterials in some of the compositions of the invention are present inamounts such that their weight plus the weight of the polyamide polymercombine to make 100% of the thermoplastic components of the compositionsof the invention. The compositions of the invention may contain variousfillers, reinforcing ingredients such as glass fibers, pigments,stabilizers, mold release agents, antistatic agents and the like all ofwhich are known to those skilled in the art.

The present invention also relates to a process for manufacturing atoughened composition, comprising:

(a) preparing an olefinic carboxylic acid or anhydride modifiedcopolymer of ethylene and one or more α-olefins having at least 4 carbonatoms/massing polymer blend to form a non-massing co-graft; and

(b) combining the non-massing co-graft produced in step (a) with (1) apolyamide material to form, under suitable reaction conditions, atoughened composition or (2) another olefinic or non-olefinic materialto form a formulation containing the non-massing co-graft.

The process more particularly comprises,

(a) preparing a modified co-graft of a blend of a copolymer of ethyleneand one or more α-olefins having at least 4 carbon atoms and a massingpolymer by (1) feeding both the massing polymer and theethylene-α-olefin at a ratio of 10-90% ethylene-α-olefin to massingpolymer into the feed throat of a 40 mm Berstorff co-rotating twin screwextruder or similar device with a barrel temperature of between 150 and400° C. (preferably 220-350° C.);

(2) optionally introducing a free radical initiator such as peroxide[0-5000 ppm] as a master batch and introduction of an olefiniccarboxylic acid or anhydride or derivative thereof in liquid form intothe extruder, to form the co-grafted polymeric blend;

(3) removing excess unreacted olefinic carboxylic acid or anhydride andisolating the polymeric co-graft; and

(b) melt-blending the polymeric co-graft produced in step (a) withpolyamide and an optional ungrafted elastomer or polyethylene in anextruder, internal mixer or rubber mill at a temperature sufficient tomelt the blend to form the toughened composition.

The process further relates to forming the toughened composition into aninjected molded material or fabricated part.

DETAILED DESCRIPTION OF THE INVENTION

As summarized above, the present invention relates to a polymericco-graft having equal or improved physical properties relative tocurrently available polyamide tougheners which also provides equal orimproved physical properties to the final toughened compositions. Inaddition, the inventors have discovered an improved process foreliminating the dusting requirement and use of a partitioning agent inthe manufacturer of acid or anhydride modified EPRs or EPDMs which arenormally susceptible to massing.

The thermoplastic polyamides used in the composition may be obtainedfrom at least one aromatic dicarboxylic acid containing 8-18 carbonatoms and at least one diamine selected from the class consisting of (i)1-12 carbon normal aliphatic straight-chained diamine, and (ii) 8-20carbon cycloaliphatic diamines containing at least one cycloaliphaticring. Diacids can be isophthalic and terephthalic acids.

Preferred diamines are hexamethylenediamine. The polyamides useful inthis invention include nylon 6,6 or nylon 6.

Processes for the preparation of toughened nylon blends are known in theart. A suitable process is disclosed, for example, in Caywood, U.S. Pat.No. 3,884,882. The compositions of this invention may be prepared bymixing preweighed, blended quantities of the polyamides and theco-grafted polymers in the molten state under high shear along withoptional ungrafted elastomers or polyethylenes. Such mixing can beaccomplished in commercially available equipment such as a 53 mmtwin-screw extruder manufactured by Werner & Pfleiderer Corporation. Asatisfactory screw design for an 1860 mm long screw includes mixingelements 750 mm and 1390 mm from the feed end of the screw. Barrelheaters may be set at 260-275° C. A vacuum port may be used near thedie. Screw speeds of 200-250 rpm and extrusion rates of 120-230 pphafford the compositions of this invention. The strands are quenched inwater and pelletized. The pellets are dried to a moisture content of0.3% by weight or less prior to final processing (e.g., injectionmolding, blow molding, extrusion). The concentrations for theingredients in toughened polyamides are at least 3 weight % co-graft and97-60 weight % polyamide. Especially preferred concentrations of theingredients in the toughened products are 15-25 wt % co-graft(toughener) and 85-75 wt % polyamide.

By “massing” is meant that the pre-modified or modified polymer absent asufficient amount of ethylene-α-olefin having at least 4 carbon atoms(including polyethylene(s)) has a tendency to mass together oragglomerate at a pressure of 100 g/sq. cm at 50° C. for a 24 hourperiod. The samples are physically inspected for massing characteristicsand are also evaluated in dry-flow experiments. In a dry-flowexperiment, 250 grams of a resin is allowed to pass through a stemmedplastic funnel (2 cm in diameter at stem) and the time to pass throughthe stem is recorded. Relative dry-flow is a good indication of howeasily the resin can be handled.

The composition of the invention may be fabricated into high impactparts such as automobile body parts, for example bumpers, fenderextensions and the like by injection molding, blow molding, extrusionand other similar techniques. Yield strength and elongation at break maybe determined according to ASTM D-638. Flexural modulus may bedetermined (¼-inch specimens) according to ASTM D-790. Notched Izodimpact (½×2.5×⅛ inch specimens) may be determined according to ASTMD-256-73. The type of specimen break may be noted as follows andconforms to definitions in ASTM D-256-73, namely:

C=complete break-wherein the specimen separates into two or more pieces

H=hinge break-an incomplete break such that one part of the specimencannot support itself above the horizontal when the other part is heldvertically

P=partial break-an incomplete break that is not a hinge break but hasfractured at least 90 percent of the distance between the vertex of thenotch and the opposite side N=non-break-an incomplete break where thefracture extends less than 90 percent of the distance between the vertexof the notch and the opposite side

M=mixed breaks-some of the samples have complete breaks and some of thesamples have partial breaks.

Notched Izod impact values may be plotted versus temperature. Theductile/brittle transition temperature is defined as that temperature atwhich half the specimens break by ductile failure and half breakcompletely. The ductile/brittle transition temperature occurs at thepoint of steepest slope on the plot of notched Izod impact value versustemperature.

The nylons containing tougheners may be tested dry-as-molded. The nylonscontaining tougheners may be conditioned in an accelerated procedure toa moisture content equivalent to 50% RH by first immersing them indemineralized water at 50° C. and then storing them in air at 23° C. and50% relative humidity until the weight gain matched that attained bylong term equilibrium exposure of such samples to air at 23° C. and 50%relative humidity.

Improvement of impact strength of polyamide resins has long been ofinterest, for resistance to shattering or brittle breaking on impact ofpolyamide molded articles is a desirable feature of any molded article.Tendency to break on impact in a brittle fashion (rather than ductilefashion), is a significant limitation on the usefulness of sucharticles. By “ductile” is meant that cracks do not tend to propagatefrom the area of impact, and thus a resin having good ductility is onethat is resistant to crack propagation caused by impact. The ductilityof an article can be measured by notched Izod test ASTM D-256-73. By“elastomeric” is meant that the copolymer after molding will assumesubstantially its original shape after distortion causing pressure isremoved. By “olefinic” is meant terminally unsaturated monomersincluding dienes and the like. By “copolymer” is meant a polymercomposed of two or more different monomeric units. EPDM used in thetables and examples stands for a copolymer composed of 72 percentethylene, 24 percent propylene, and 4 percent 1,4-hexadiene. It isemployed as an extender for the toughening polymer.

The present invention is alternatively directed to a polymeric co-graftcomposition, comprising

(a) an elastomer having a density of less than 0.88 wherein theelastomer has a tendency to mass; and

(b) an olefinic polymer having a density range of 0.88 to 0.93 wherein

(a) and (b) are co-grafted with a grafting monomer selected from anolefinic carboxylic acid or anhydride at a percentage-by-weight of 0.05to 5%.

Grafting or modification of EPDM or other elastomer subject to massingor characterized as having massing tendencies along with PE results inan adduct blend having 0.05 to 5%, preferably 0.1-3% and most preferablyfrom 0.3-2% functionality, acid or anhydride or both, as can be measuredby Infrared (CPE 671 Spectrophotometer), and 0.05-5 dg/min melt flow at190° C. through a 0.0825″ in diameter orifice under a weight of 2.16 Kg.Preferably, the melt flow is 0.1-10 dg/min, most preferably 0.5-5dg/min.

The present invention more particularly comprises a thermoplasticpolyamide blend comprising:

(a) 60-97% by weight of a polyamide;

(b) 3-40% by weight of a polymeric, toughening agent co-graftcomposition that is prepared from a blend of a massing polymer and apolyethylene.

The thermoplastic polyamide may be selected from Nylon 6,6 or nylon 6 orblends thereof. Nylon 6,6 is polyhexamethyleneadipamide, while nylon 6is polycaprolactam. Both are high molecular weight polymers, i.e., offilm-forming molecular weight. The invention further comprises (a)60-97% by weight of a olefinic or non-olefinic material; and (b) 3-40%by weight of a polymeric co-graft (Composition A) that is prepared froma blend of a massing polymer and a polyethylene.

The carboxyl or carboxylate functionality is ordinarily supplied byemploying as grafting reagent an ethylenically unsaturated compoundcontaining carboxyl or carboxylate groups. The carboxyl or carboxylatefunctionality can be supplied by reacting the massing polymer andpolyethylene blend with an unsaturated compound taken from the classconsisting of alpha, beta-ethylenically unsaturated dicarboxylic acidshaving from 4 to 8 carbon atoms, or derivatives thereof. Suchderivatives include monoesters of alcohols of 1 to 29 carbon atoms,anhydrides of the dicarboxylic acids, or the metal salts of the acids,or the monoester of the dicarboxylic acid having from 0 to 100 percentof the carboxylic acid groups ionized by neutralization with metal basicsalt, and the like. Illustrative of such acids and derivatives aremaleic acid, maleic anhydride, maleic acid monoethyl ester, metal saltsof maleic acid monoethyl ester, fumaric acid, fumaric acid monoethylester, itaconic acid, vinyl benzoic acid, vinyl phthalic acid, metalsalts of fumaric acid monoethyl ester, monoesters of maleic or furmaricacid or itaconic acids where the alcohol is methyl, propyl, isopropyl,butyl, isobutyl, hexyl, cyclohexyl, octyl, 2-ethyl hexyl, decyl,stearyl, methoxy ethyl, ethoxy ethyl, hydroxy or ethyl, and the like.The adducts can be prepared by any grafting process which intimatelymixes the unsaturated acid or derivatives with the polymeric blend (suchas EPDM or EPR and PE) without appreciable generation of free radicals,and which concurrently or subsequently heats the mixture to atemperature where thermal addition occurs. Selected temperatures willgenerally be at least 225° C. to obtain adduct formation at acceptablerates and less than about 450° C. to avoid any excessive polymerbreakdown.

Preferred temperature ranges will vary with the particular polymer andcan readily be determined by one skilled in the art. Mixing of the acidor derivative and polymer can be by blending in an internal mixer orextruder, or by blending finely divided dry compound with polymer on awell-ventilated rubber mill with concurrent or subsequent heating, suchas in a hot press or mold. The acid or derivative can be substitutedwith groups, such as bromine or chlorine, which do not unduly interferewith the graft reaction.

It is generally desired to form adducts containing about 0.05 to 5percent, and preferably about 0.1 to 3 percent, by weight of thegrafting monomer incorporated.

Representative massing polymers include those metallocene ornon-metallocene ethylene propylene diene rubbers and ethylene propylenerubbers or polymers selected from copolymers of ethylene and α-olefinswith at least 3 carbon atoms which have a density of less than 0.88 g/ccor as described in the examples. Metallocene substantially linearethylene copolymers described in U.S. Pat. No. 5,346,963 arespecifically incorporated herein provided that such polymers have therequisite density and/or massing tendencies either before grafting orpost-grafting with olefinic carboxylic acid or anhydride compounds. Thisspecifically includes substantially linear ethylene-octene copolymershaving a melt flow ratio of I₁₀/I₂ of equal or greater than 6.13 and aM_(w)/M_(n) ratio of equal or less than the melt-flow ratio less 4.63.Such metallocene polymers are commercially available and sold byDuPont-Dow under the trademark ENGAGE®. Other suitable massing polymersinclude those metallocene polymers having the requisite density and/ormassing characteristics but with a melt-flow ratio I₁₀/I₂ of less than6.53 and an M_(w)/M_(n) ratio of greater than the melt flow ratio less4.63. Such polymers are commercially available under the trademarkEXACT® by Exxon.

The polyethylenes suitable for the pregrafted blend with the massingpolymer are selected from copolymers of ethylene with one or moreα-olefins having at least 4 carbon atoms, e.g., ethylene butene-1copolymer, ethylene-hexene-1 copolymers, ethylene-octene-1 copolymers,ethylene-butene-octene terpolymer where its density lies between 0.880to 0.930 g/cc, preferably 0.890 to 0.920 g/cc, and most preferably,0.900 to 0.910 g/cc. The preferred melt index (MI) is (at 190° C., 2.16Kg) is between 0.01 to 50 dg/min, more preferred is between 0.1 to 10dg/min, and most preferred 0.5 to 5 dg/min. The polyethylene can be madeusing conventional Zeigler Natta catalyst or using known metallocenecatalysts.

The toughening material blends of the present invention are prepared byadmixing the ingredients in the indicated proportions and melt blendingthem for intimate admixture. Preferably, the nylon 6, nylon 6,6 andtoughening polymer or polymers are first mixed by tumbling in a drum.The melt blending typically can be conducted at a temperature above themelting point of the components and below the decomposition temperature.A temperature range of about from 260° C. to 330° C. is preferred.

The toughening blends are particularly useful in applications in whichimpact strength is important at low temperatures, such as in automobilebumpers, sports equipment, safety equipment and the like. The blends ofthis invention may also contain one or more conventional additives suchas stabilizers and inhibitors of oxidative, thermal, and ultravioletlight degradation, lubricants and mold release agents, colorantsincluding dyes and pigments, flame-retardants, fibrous and particulatefillers and reinforcements, plasticizers, and the like. These additivesare commonly added during the mixing step.

Representative oxidative and thermal stabilizers which may be present inblends of the present invention include Group I metal halides, e.g.,sodium, potassium, lithium with cuprous halides, e.g., chloride,bromide, iodide; hindered phenols, hydroquinones, and varieties ofsubstituted members of those groups and combinations thereof.Representative ultraviolet light stabilizers, include varioussubstituted resorcinols, salicylates, benzotriazoles, benzophenones, andthe like.

Representative lubricants and mold release agents include stearic acid,stearyl alcohol, and stearamides. Representative organic dyes includenigrosine, while representative pigments, include titanium dioxide,cadmium sulfide, cadmium selenide, phthalocyanines, ultramarine blue,carbon black, and the like.

Representative fillers include carbon fibers, glass fibers, amorphoussilica, asbestos, calcium silicate, aluminum silicate, magnesiumcarbonate, kaolin, chalk, powdered quartz, mica, feldspar, and the like.

Representative flame-retardants include organic halogenated compoundssuch as decabromodiphenyl ether and the like. Aluminum distearates mayalso be added.

As discussed above, the toughening composition consists essentially of aco-grafted blend of polyethylene and any known massing polymers whichexhibit massing problems. Surprisingly, the inventors have discoveredthat addition of a sufficient quantity of PE in the density range of0.880-0.930 g/cc to ungrafted or unmodified rubbers such as EPDM or EPRor those metallocene polymers which are susceptible to massing followedby grafting using typical grafting agents selected from, for example,maleic acid or anhydride, eliminates the requirement of dustingmaterials (partitioning reagents) which heretofore were required forthese materials without diminishing their toughening properties inpolyamide blends containing said composition.

Variables that an artisan will recognize include relative PEconcentration ranges; density ranges of the PE and the graft level (%)ranges of the blend. The PE concentration (weight percentage relative tothe EPDM or other polymer) should be sufficient to provide non-massingcharacteristics to the blend while still permitting sufficient EPDM andthus grafted EPDM to provide toughening properties to the polyamide ormaterial requiring toughening. A suitable weight percentage of PE isgreater than 10% and less than 90% wherein this blend (PE/EPDM orPE/EPR), upon grafting with a suitable grafting agent, has non-massingcharacteristics and toughening characteristics.

The compositions of the invention farther comprise or consistessentially of a graft modified polymeric blend made from (a) PE in aweight percentage ratio relative to (a)+(b)+(c) of greater than 10%; (b)EPDM or other polymer which is susceptible to massing and (c) a graftingagent. The density ranges and graft level ranges of the PE and thePE/pre-grafted toughener varies with known PE densities and knowntoughener grafting percentages wherein said densities and graftinglevels provide sufficient toughening properties and do not disrupt thenon-massing influence of the PE.

For performance as a toughener, the following variables should bemanipulated:

Variable preferred trend PE concentration low PE density low graft levelhigh

For selection of non-massing characteristics, the following variablesshould be manipulated:

PE concentration high PE density high graft level no effect

Without being bound by theory, it is also possible that the ability ofthe PE to make the EPR or massing polymer non-massing depends on thecrystallinity of the EPR or massing polymer. The present invention inone aspect preferably relates to a method of improving the massingcharacteristics of semi-crystalline massing polymers comprising adding anon-massing effective amount of polyethylene to said elastomer followedby co-grafting.

The polyamide matrix resin of the toughened compositions of thisinvention is well known in the art and embraces those semi-crystallineand amorphous resins having a molecular weight of at least 5000 andcommonly referred to as nylons. Suitable polyamides include thosedescribed in U.S. Pat. Nos. 2,071,250; 2,071,251; 2,130,523; 2,130,948;2,241,322; 2,312,966; 2,512,606; and 3,393,210. The polyamide resin canbe produced by condensation of equimolar amounts of a saturateddicarboxylic acid containing from 4 to 12 carbon atoms with a diamine,in which the diamine contains from 4 to 14 carbon atoms. Excess diaminecan be employed to provide an excess of amine end groups over carboxylend groups in the polyamide. Examples of polyamides includepolyhexamethylene adipamide (66 nylon), polyhexamethylene azelaamide (69nylon), polyhexamethylene sebacamide (610 nylon), and polyhexamethylenedodecanoamide (612 nylon), the polyamide produced by ring opening oflactams, i.e., polycaprolactam, polylauric lactam,poly-11-amino-undecanoic acid, bis(paraaminocyclohexyl) methanedodecanoamide.

It is also possible to use in this invention polyamides prepared by thecopolymerization of two of the above polymers or terpolymerization ofthe above polymers or their components, e.g., for example, an adipic,isophthalic acid hexamethylene diamine copolymer. Preferably thepolyamides are linear with a melting point in excess of 200° C. As greatas 97 percent by weight of the composition can be composed of polyamide;however, preferred compositions contain from 60 to 85 percent, and morenarrowly 75 to 85 percent, by weight of polyamide.

The toughened composition or pre-fabricated material is toughened orstrenghthend by the combination of at least one polymer and PE which isultimately grafted with the above grafting agent and further added topolyamide or other material. The term “at least one polymer” means oneor more polymers which coexist in single discrete particles having aparticle size ranging from 0.01 to 3 microns, preferably 0.02 to 1micron, within the matrix, so that either the mixture of polymers or atleast one of the polymers in the mixture meets the following criteria.

(a) sites which adhere to the polyamide matrix;

(b) tensile modulus, as added in the range of about 1.0 to 20,000 psi.,preferably about 5 to 20,000 psi., the ratio of tensile modulus of thepolyamide matrix resin to tensile modulus of said at least one polymerbeing greater than 10 to 1, preferably greater than 20 to 1.

The polyamide is the continuous phase in the composition and the polymerperforms the function of a soft dispersed phase which is adhered to thepolyamide matrix.

The melt flow of the co-grafted composition is in the range of 0.05-50dg/min by ASTM D-1238 at 190° C. though a 0.0825″ diameter orifice and2160 g. load, preferably 0.1 to 10 dg/min and most preferably 0.5-5dg/min. Since the viscosity is highly shear sensitive the compositionsof the invention are well suited for extrusion applications.

It is apparent from the above description that a variety of co-graftedpolymeric blends are effective in toughening polyamides or in improvingproperties of other olefinic or non-olefinic materials and asubstantially large number of combinations are useful. It is thereforenot surprising that the limits of effectiveness of some components ofthe compositions depend on the other components. For example, the lowerlimit of concentration of an effective adhering site, e.g., maleicanhydride, will probably be lower than a less effective adhering site,e.g., methacrylic acid. Similarly the balance between amine and carboxylend groups in a matrix will influence the comparative effectiveness ofdifferent adherent sites of the at least one polymer. Polymers orpolymeric mixtures in the lower modulus range tend to be more effectivethan those polymers or polymeric mixtures in the higher modulus rangeand may be useful at lower concentrations of adherent site. However,more than one such polymeric mixture can be present in the toughenedthermoplastic composition.

Stabilizers can be incorporated into the composition at any stage in thepreparation of the thermoplastic composition. Preferably the stabilizersare included early to preclude the initiation of degradation before thecomposition can be protected. Such stabilizers must be compatible withthe composition. The oxidative and thermal stabilizers useful in thematerials of the present invention include those used in additionpolymers generally. They include, for example, up to 1 percent byweight, based on the weight of polyamide of Group I metal halides, e.g.,sodium, potassium, lithium with cuprous halides, e.g., chloride,bromide, iodide, hindered phenols, hydroquinones, and varieties ofsubstituted members of those groups and combinations thereof.

The ultraviolet light stabilizers, e.g., up to 2.0 percent, based on theweight of polyamide, can also be those used in addition polymersgenerally. Examples of ultraviolet light stabilizers include varioussubstituted resorcinols, salicylates, benzotriazoles, benzophenones, andthe like. Abbreviations for some of the terms specified herein include:

PE-polyethylene

EPR-ethylene/propylene rubber

EPDM-ethylene/propylene/diene rubber

mPE-metallocene catalyzed polyethylene.

The following examples describe the various co-grafted blends andcompositions which were made according to the invention and further showthe physical properties associated with each composition that relate toadvantageous performance. They are to be construed as non-limiting. Inaddition to the compositions described herein, the present inventionrelates to a process for the preparation of a toughened multi-phasethermoplastic composition which comprises, in a closed system, (a)admixing (1) 60 to 97 percent by weight of a polyamide matrix resin ofnumber average molecular weight of at least 5000, and (2) 3 to 40percent by weight of at least one co-grafted polymeric blend at atemperature in the range of about 5° to 100° C. above the melting pointof said polyamide matrix resin and (b) shearing to disperse the polymerin said matrix.

EXAMPLES

The examples in Tables 1 and 2 were made by feeding both the massingpolymer (EPDM) and PE together at the indicated ratios into the feedthroat of a 40 mm Berstorff co-rotating twin screw extruder with thebarrel temperature set at 280° C. Peroxide (300 ppm) was then introducedin the form of a master batch and the maleic anhydride (1-2% by weightrelative to total polymer feed) is added as a liquid and injected intothe extruder through an injection port. After the reaction, theunreacted grafting monomer is removed by applying vacuum at a vent port.The resulting product was pelletized by using a Gala under waterpelletizer and collected into bags.

The following Table shows the improvement of non-massing characteristicswith the incorporation of PE in feed:

TABLE 1 Co-graft Composition MI (190 C.) MA Dry flow Massing Example EPR% PE type PE % dg/min. % sec 50 C., 24 hr.  1 78 PE 1 22 4.6 0.92 36none  2 76 PE 1 24 3 1.2 22 none  3 47.5 PE 1 52.5 0.95 1 5.7 none  447.5 PE 1 52.5 1.7 0.89 5.8 none  5 19 PE 1 81 0.9 0.82 5.5 none  6 19PE 1 81 0.49 1.27 5.8 none  7* 0 PE 1 100 0.43 1.41 5.4 none  8* 0 PE 1100 0.43 0.92 5.3 none  9 76 PE 2 24 4.1 0.96 18 none 10 76 PE 2 24 3.21.38 16 none 11 47.5 PE 2 52.5 2 1.2 7.6 none 12 47.5 PE 2 52.5 2.8 0.848.3 none 13 19 PE 2 81 1.5 0.91 6.2 none 14 19 PE 2 81 1.1 1.33 6.3 none15 0 PE 2 100 1 1.4 6.4 none 16 0 PE 2 100 1.21 0.91 6.4 none  17* 100 06.9 0.67 48 massed 18 76 PE 3 25 4.7 1.03 89 breakable 19 76 PE 3 24 3.21.26 61 breakable 20 47.5 PE 3 52.5 2.5 1.05 40 none 21 19 PE 3 81 3.80.89 31 none 23 19 PE 3 81 2.3 1.17 28 none  24* 0 100 2.4 1.24 30 none 25* 0 100 3.6 0.91 34 none 26 85.5 PE 3 14.5 5.6 1.08 82 massed,breakable 27 90 PE 3 10 9.1 0.84 109 massed  28* 95 5 5.8 1.13 47massed, breakable *= comparative

The massing tendencies were evaluated by subjecting the polymer under apressure of 100 g/sq. cm at 50° C. for a period of 24 hr. The pressureis similar to the one experienced by the bottom layer of a 1 ton palletof resins. At the end of the period, the polymer was inspected to see ifthe pellets have massed together and if so, whether the mass can bebroken up.

In the dry flow experiment, 250 g of the resin was allowed to passthrough a stemmed plastic funnel (diameter of the Stern is about 2 cm).The time it took for the resin to pass through was recorded This time isdependent on the shape of the pellets, but since all the samples areproduced under similar conditions, their shapes are similar. Therelative dry flow time is therefore a good indication of how easy theresin can be handled.

The above examples demonstrate that the presence of the PE in thesystems helps minimize the massing tendencies of the co-grafts andimproves their dry flow characteristics. In the absence of any PE, theproduct massed badly and had a very slow Dry flow (Ex. 17) The presenceof small amount of PE (5%, Ex. 28) still resulted in massing. Additionof 22 or more % of a LLDPE (PE 2, 0.920 density) or HDPE (PE 1, 0.956density) rendered the product non-massing and with good dry flowproperties. However, the addition of up to 24% of a VLDPE (PE 3, 0.885density) did not make the product non-massing, although the mass waseasily breakable. With this lower density PE, addition of up to 52% isrequired to make it truly non-massing.

The toughening characteristics of the polymer mix depends on the densityof the PE. The higher the density of the PE, the smaller amount of PE istolerable in the blend.

It may be seen by inspection from the table that lower PE densityproduces better results. PE 1 gave supertough impact only when it wasless than 20% of the recipe. PE 2 gives supertough results at 23° C.,but many of the 0° C. breaks were brittle. PE 3 gave uniformly ductilebreaks.

The toughening characteristics also depend upon the graft level of themodified Polymer blend. Higher graft level is required when the PEdensity is higher.

The following examples demonstrate the effectiveness of adding anethylene-α-olefin having at least 4 carbon atoms copolymer (includingterpolymers) with a density range of 0.880 to 0.930 g/cc and an MI (190°C., 2.16 Kg) of between 0.01 to 50 dg/min in a percentage of >10% to ametallocene produced polymer having a tendency to mass. The resultsclearly show the non-massing characteristics of the resulting co-graftedproduct. The co-grafted compositions are effective as tougheners inpolyamide compositions wherein said co-graft is present in a percentageof 3-89% of the co-graft/polyamide blend.

Example 29

20% Ethylene/butene/octene terpolymer (density 0.91 g/cc, 1.9 MI) and80% of metallocene ethylene octene polymer (density 0.857 g/cc, 1 MI)were co-grafted together with maleic anhydride in a 43 mm Berstorffco-rotating twin extruder in the presence of 300 ppm Lupersol 101 at260° C. The co-graft had an MA level of 0.55% and an MI of 2.2 dg/min.

Example 30

The same procedure described in 29 above was used except that 40% of thePE terpolymer was used instead of 20%. The co-graft had a graft level of0.45% and an MI of 1.7 dg/min.

Comparative Example (metallocenes)

Ethylene/octene copolymer—(density 0.857 g/cc, 1 MI) was grafted withmaleic anhydride in a 43 mm Berstorff co-rotating twin extruder in thepresence of 300 ppm of Lupersol 101 at 260° C. The product waspelletized using a Gala underwater pelletizer and collected in a paperbag. It had a 0.59% maleic anhydride incorporation and an MI of 2.4.

Comparative Example (metallocene) exhibited massing characteristicsovernight while Example 29 and 30 did not mass.

Example 31

A blend of an ethylene/butene/octene terpolymer (0.910 density, 1.9 MI)and a copolymer of ethylene/butene (0.863 g/cc, 0.5 MI) at a ratio of 80to 20 by weight was grafted with maleic anhydride in a process similarto Example 30 above. The product had a graft level of 0.9% and an MI of2 dg/min and was non-massing.

This example demonstrates that even high levels of an ethylene-α-olefinhaving at least 4 carbon atoms copolymers (including terpolymers) whenco-grafted with a metallocene ethylene octene substantially linearpolymer with a density of 0.863 g/cc and an MI of 2 dg/min provides anon-massing co-graft. This co-graft was then blended with a polyamideand provided good toughening characteristics.

Examples 32-63 below demonstrate the preparation of a non-massingco-graft followed by addition of a co-graft to a polyamide to form atoughened composition.

Example 32

A mixture of 47.5% NORDEL® 3681, 47.5% PE ( 0.905 density, 0.8MI, Attane4403) and 5% of peroxide concentrate (5500 ppm of Lupersol 101 in aVLDPE) was grafted with 2% maleic anhydride in a co-rotating twin screwextruder at 310° C. NORDEL® 3681 is an EPDM available commercially fromDuPont/Dow Elastomers Co., Wilmington, Del. Attane 4403 is a DowChemical Company's Ultra Low Density Ethylene Octene Copolymer. Lupersol101 is 2,5-dimethyl 2,5di(t-butylperoxy)hexane, a registration trademark of Elf Ato Chem. The product has a MI of 0.9 dg/min. at 1 90° C.and a graft level of 1.46%.

The product described and the other co-grafts prepared were melt blendedtogether with nylon 6,6 (available commercially from E. I. du Pont deNemours and Company, Wilmington, DE as ZYTEL®& 101), and NORDEL® 3681using 16.1 lbs. polyamide, 3.9 lbs. co-graft and 9.1 g aluminumdisteareate. During the operation for melt blending of the toughenerwith the polyamide, the ingredients were first dry blended by tumblingin a drum. The mixture was then compounded by melt blending in a 30 mmWerner & Pfleirerer co-rotating twin screw extruder with a barreltemperature of between 230° C. and 260° C. and a die temperature of 290°C. Extrusion was carried out with a port open to the air or undervacuum. The screw speed was 360 rpm and the extruder feed rate was56+pounds per hour. The resulting strand was quenched in water, cut intopellets, and sparged with nitrogen until cool. The moisture in theresulting pellets was adjusted to between 0.1% and 0.2% by drying oradding additional water as required. Test bars (½×2.5×⅛ inch) weremolded in an injection molding machine. The molded bars were testedusing the Notched Izod testing procedure ASTM D-256-73 in theirdry-as-molded state.

The following examples were prepared as above and Table 2 shows theresults

TABLE 2 Example (Toughened Composition) Co-graft % MA PE Type PE Den %PE. % EPR % PO NI 0 NI 23 33 28 1.13 NONE 0 95 13.95 17.05 34 27 0.84 PE3 0.885 10 90 0 13.94 15.49 35 26 1.08 PE 3 0.885 9.5 85.5 5 15.12 18.3436 25 0.91 PE 3 0.885 95 0 5 11.32 16.84 37 24 1.24 PE 3 0.885 95 0 514.46 18.89 38 23 1.17 PE 3 0.885 76 19 5 14.81 18.66 39 22 0.89 PE 30.885 76 19 5 12.92 17.09 40 21 0.82 PE 3 0.885 47.5 47.5 5 15 17.93 4120 1.05 PE 3 0.885 47.5 47.5 5 14.25 18.32 42 19 1.26 PE 3 0.885 19 76 516.14 19.11 43 18 1.03 PE 3 0.885 19 76 5 16.32 18.47 44 17 0.67 NONE 0100 0 14.66 15.05 45 16 0.91 PE 2 0.92 95 0 5 3.53 4.65 46 15 1.4 PE 20.92 95 0 5 4.55 15.87 47 14 1.33 PE 2 0.92 76 19 5 5 16.15 48 13 0.91PE 2 0.92 76 19 5 3.59 12.23 49 12 0.84 PE 2 0.92 47.5 47.5 5 5.68 15.4650 11 1.2 PE 2 0.92 47.5 47.5 5 8.99 17.5 51 10 1.38 PE 2 0.92 19 76 516.19 18.87 52 9 0.96 PE 2 0.92 19 76 5 14.84 19.25 53 8 0.92 PE 1 0.95695 0 5 2.54 2.74 54 7 1.41 PE 1 0.956 95 0 5 3.14 3.37 55 6 1.27 PE 10.956 76 19 5 3.28 3.6 56 5 0.82 PE 1 0.956 76 19 5 2.42 2.7 57 4 0.89PE 1 0.956 47.5 47.5 5 3.46 4.19 58 3 1 PE 1 0.956 47.5 47.5 5 3.87 4.8259 2 1.2 PE 1 0.956 19 76 5 7.25 17.59 60 1 0.92 PE 1 0.956 19.5 78 2.55.89 16.51

In addition to the examples prepared above, the toughened polyamidecompositions were also diluted with EPDM to determine the effect. Table3 shows the relative ingredient ratios and the NI resulting using NItest ASTM D-256-73.

The NI of the resulting blends are summarized as follows:

TABLE 3 Example modified (Toughened Nylon (EPDM/ Composition) 6,6 PE)EPDM NI@23° C. NI@0° C. 61 80.5% 13% 6.5% 18.94 14.1 62 80.5% 11.7% 7.8%18.25 14.0 63 80.5% 9% 10.5% 16.69 6.72

The results indicate that good room temperature and low temperatureNotched Izod values are obtained even when the graft source is dilutedwith EPDM. (EPDM/PE)-g-MA and PE together as a toughener blend may alsobe utilized according to the method described herein.

In addition to the advantages described heretofore, the co-graftedpolymers have enhanced melt-cutting properties, better ease of handlingand enhanced pelletization properties.

What is claimed is:
 1. A polymeric toughening agent useful for improvingthe impact properties of polymeric compositions, comprising, (a) acopolymer of ethylene with one or more α-olefins having at least 4carbon atoms and having a density of 0.930 to 0.880 g/cc and a meltindex (MI) of 0.01 to 50 dg/min at 190° C., 2.16 Kg; (b) a massingpolymer selected from a copolymer of ethylene with one or more α-olefinshaving at least 3 carbon atoms and having a density of 0.850 to 0.880g/cc and an MI of 0.01 to 50 dg/min at 190° C., 2.16 Kg wherein theratio of (a) to (b) is 10:90-90:10; and (c) 0.9-5 wt % relative to (a)and (b) of a grafted monomer covalently bonded to (a) and (b) selectedfrom an olefinic carboxylic acid or anhydride or derivative thereof. 2.The polymeric toughening agent of claim 1 wherein component (a) has adensity of 0.890 to 0.920 g/cc and an MI of 0.1 to 10 dg/min andcomponent (b) has a density of 0.855 to 0.875 g/cc and an MI of 0.1 to10 dg/min.
 3. The polymeric toughening agent of claim 1 whereincomponent (a) has a density of 0.890 to 0.920 g/cc and an MI of 0.1 to10 dg/min and component (b) has a density of 0.855 to 0.875 g/cc and anMI of 0.1 to 10 dg/min and wherein component (c) is 0.1 to 3 wt %relative to (a) and b).
 4. The polymeric toughening agent of claim 1wherein component (a) has a density of 0.90 to 0.910 g/cc and an MI of0.5 to 5 dg/min and component (b) has a density of 0.86 to 0.87 g/cc andan MI of 0.4 to 2 dg/min.
 5. The polymeric toughening agent of claim 1wherein component (a) has a density of 0.90 to 0.910 g/cc and an MI of0.5 to 5 dg/min and component (b) has a density of 0.86 to 0.87 g/cc andan MI of 0.2 to 2 dg/min and wherein component (c) is 0.9 to 2 wt %relative to (a) and (b).
 6. The polymeric toughening agent of claim 1wherein component (a) is selected from a linear low density polyethyleneand component (b) is selected from an ethylene/propylene/diene monomer,ethylene/propylene rubber; a metallocene polyethylene having a melt flowratio I₁₀/I₂ of less than 6.53 and an M_(w)/M_(n) ratio of greater thanthe melt flow less 4.63; a metallocene polyethylene having a melt flowratio I₁₀/I₂ of less than 6.13 and an M_(w)/M_(n) ratio of equal or lessthan the melt flow ratio less 4.63 and component (c) is selected fromthe group consisting of acrylic acid, methacrylic acid, fumaric acid,maleic acid, nadic acid, citaconic acid, itaconic acid and anhydrides,metal salts, esters, amides or imides of said salts.
 7. The polymerictoughening agent of claim 6 wherein the toughening agent is non-massing.8. A polymeric composition having improved impact properties,comprising: (1) a polymeric toughening agent useful for improving theimpact properties of the polymeric composition, comprising, (a) acopolymer of ethylene with one or more α-olefins having at least 4carbon atoms and having a density of 0.930 to 0.880 g/cc and an MI of0.01 to 50 dg/min at 190° C., 2.16 Kg; (b) a massing polymer selectedfrom a copolymer of ethylene with one or more α-olefins having at least3 carbon atoms and having a density of 0.850 to 0.880 g/cc and an MI of0.01 to 50 dg/min at 190° C., 2.16 Kg wherein the ratio of (a) to (b) is10:90-90:10; and (c) 0.9-5 wt % relative to (a) and (b) of a graftedmonomer covalently bonded to (a) and (b) selected from an olefiniccarboxylic acid or anhydride or derivative thereof; and (2) an olefinicor non-olefinic material.
 9. The polymeric composition of claim 8wherein the non-olefinic material is selected from a polyamide andwherein the weight percentage ratio of (1):(2) is 3-40:97-60.
 10. Thepolymeric composition of claim 9 wherein the polyamide is selected fromnylon 6 or nylon 6,6 and wherein the weight percentage ratio of (1):(2)is 15-25:85-75.
 11. A process for producing a polymeric compositionhaving improved impact properties, comprising, (a) preparing a polymerictoughening agent useful for improving the impact properties of thepolymeric composition as claimed in claim 1, by: (1) feeding both amassing polymer and an ethylene-α-olefin at a ratio of 10-90 wt %ethylene-α-olefin to massing polymer into the feed throat of a twinscrew extruder at a barrel temperature of 150-400° C.; (2) optionallyintroducing a free radical initiator and introducing an olefiniccarboxylic acid or anhydride or derivative thereof into the extruder toform the polymeric toughening agent; (3) removing excess unreactedolefinic carboxylic acid or anhydride and isolating the polymerictoughening agent; and (b) melt-blending the polymeric toughening agentproduced in step (a) with a polyamide or another non-olefinic orolefinic material in an extruder, internal mixer or rubber mill at atemperature sufficient to melt the blend to form the polymericcomposition.
 12. The process according to claim 11 wherein apartitioning agent is not required to eliminate or diminish massing ofthe massing polymer.
 13. The process of claim 11 wherein the olefiniccarboxylic acid or anhydride is maleic anhydride and the polyamide isselected from nylon 6,6 or nylon
 6. 14. Fabricated articles made fromthe polymeric composition of any one of claim 8 or 9.